Delayed cabin heat and red triangle accompanied by a thermostat symbol

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by KJP, Feb 11, 2016.

  1. KJP

    KJP Junior Member

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    My 06 prius takes a very long time to provide heat to the cabin. In temps below 20 F it can take 20 minutes. Today in 16 F weather the red triangle came on, followed by a problem banner, followed by a thermostat symbol. The triangle and symbol turned on a off a couple of times over a 5 minute span. I had been driving the car from a cold start for about 15 minutes when this happened. The car did start to produce some, but not a lot, of heat at about 20 minutes into the drive. I was also forced to use the defroster intermittently for the first 15 minutes (blew only cold air). After parking the car for 20 minutes I drove 20 minutes home with no triangle or thermostat symbol. Most of the way home I had sufficient heat.

    I do have the front blocked with pipe insulation.
    I have owned my 06 prius for over a year and it has 257,000 on it.

    Could the thermostat and triangle be caused by a low engine temp? If so would a stuck thermostat be a potential culprit?

    Can I assume that if my car is blowing cold air when I am asking for heat that the engine is not over heating?

    Do I need to do anything special while working on the coolant system to not upset the touchy computers?

    Any helpful thoughts would be great.
     
  2. bisco

    bisco cookie crumbler

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    i would start by having the codes read, or getting mini vci if you plan on doing work yourself.
     
  3. Dion Kraft

    Dion Kraft Member

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  4. andrewclaus

    andrewclaus Active Member

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    I'm going to guess there's something wrong with the coolant level or the heater circulating pump (there's an electric pump for the heater core, not the engine coolant pump). I think the warning lights you're getting are for high temps, not low temps. I would definitely not block air flow at the grille.

    Have you checked coolant level in the COLD radiator (not the plastic reservoir--you need to pull the black cover over the radiator cap). If there's air in the system, it's very difficult to bleed on this car. There are other threads here about that.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    No, you cannot make that assumption. In fact the most likely cause of your symptoms is that you lack sufficient coolant in the radiator and/or have air in the cabin heater core. That is causing the lack of cabin heat and the engine overheating warning.

    See if your engine coolant pump is leaking coolant out of the pump shaft bearing. Typically this is manifested by a pinkish stain upon the AC compressor housing, on the inside of the pump pulley, possibly sprayed on the underhood sound insulation pad, etc. If so, replace the coolant pump.

    The only thing special is that you need to do a very good job getting air out of the engine coolant loop. I have posted on how to do that and on how to run the coolant heat recovery system pump manually to fill the CHRS canister, if you do not have Mini VCI to run the pump via software command.
     
  6. ChapmanF

    ChapmanF Senior Member

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    I was once driving up through Chicagoland in a car borrowed from a friend, which turned out to lose coolant. Got through town finally, up by the botanical gardens, glanced down at the dash and saw the temp gauge nearly pegged hot.

    So I reached down immediately and turned the heat up full blast (in August...) just to extract some more heat that way, and ... no heat came out. Bad sign ... too little coolant to even circulate to the cabin. Next move was quick exit and pull off the road....

    -Chap
     
  7. Dion Kraft

    Dion Kraft Member

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    The next worse thing is that your gauge starts to go to cooler meaning that coolant is no longer being read but only HOT vapor is passing by the sensor which it cannot read.. Next Stop Blown Head gaskets!
     
  8. DreadPiratePatty

    DreadPiratePatty Junior Member

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    Did you ever discover the source of this problem? I have the exact symptoms and have already replaced the coolant pump after it threw the code indicating there was an issue with it. When it was pulled there were stains from a leak.
     
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